The present invention relates to the monitoring of call signaling in a telecommunications network, and more particularly to methods and systems for observing, analyzing and correlating a sequence of call signaling messages associated with a particular mobile call whereby information contained in one monitored signaling message is used to locate another signaling message in the call trace sequence.
A typical wireless or cellular telecommunications network, generally indicated by the numeral 100, is illustrated in FIG. 1. More particularly, the wireless communication network 100 presented in FIG. 1 is an example of simplified global system for mobile communication (GSM)-type network. Sample GSM network 100 includes a telecommunication terminal or telephone handset 102, a base station system (BSS) 104, a mobile switching center (MSC) 106, a home location register (HLR) 108, and an authentication center (AuC) 110.
Mobile switching center (MSC) 106 is the functional entity that represents an automatic packet switching system within a wireless communication network. When such a packet switching system is implemented so as to serve as the interface for user traffic between the cellular network and other public switched networks, the corresponding node is often referred to as a Gateway MSC or GMSC. In general, MSC 106 provides basic switching functionality and coordinates the establishment of calls between wireless end users. An MSC is directly responsible for transmission facilities management, mobility management, and call processing functions. An MSC node is typically in communication with the air-interface components of a wireless network (i.e., base station systems) as well as with other voice and signaling related nodes in the wireless network. As such, an MSC incorporates switching functions, mobile application functions, and other service logic functions in a wireless communications network.
Home location register (HLR) 108 is the functional entity that represents the primary database repository of subscriber information used to provide control and intelligence in wireless communication networks. The term register denotes control and processing center functions as well as the database functions. An HLR is managed by the wireless service provider and represents the xe2x80x9chomexe2x80x9d database for subscribers who have subscribed to service in a particular geographic area. An HLR contains a record for each xe2x80x9chomexe2x80x9d subscriber that includes location information, subscriber status, subscribed features, and directory numbers. Supplementary services or features that are provided to a subscriber are ultimately controlled by an HLR. HLR nodes typically incorporate database functions, mobile application functions, as well as other service logic functions, and may service one or more MSCs.
Authentication center (AuC) 110 is the functional entity that represents the authentication functions used to verify and validate a mobile subscriber""s identity. An AuC node manages and processes authentication information related to a particular mobile subscriber. Typically, this information consists of encryption and authentication keys as well as complex mathematical algorithms used to prevent fraudulent or unauthorized use of the wireless network. An AuC incorporates database functions used for the authentication keys and authentication algorithm functions.
Those skilled in the art of GSM communication networking will appreciate that the network elements described above represent only a few of the network entities that are commonly deployed in a GSM network. It will also be appreciated that such GSM-type network elements are communicatively coupled via a variety of communication link types, which in turn may employ a variety of signaling application and transport protocol suites. As illustrated in FIG. 1, BSS 104 is communicatively coupled to GMSC node 106, while GMSC node 106 is further coupled to both HLR node 108 and AuC node 110.
The establishment and maintenance of a call to or from mobile handset 102 typically involves the use of a number of signaling messages that are communicated between various network entities that comprise the GSM network 100. For instance, BSS 104 communicates with GMSC node 106 using both direct transfer application protocol (DTAP) and base station system management application protocol (BSSMAP) signaling protocol messages which may be transmitted over inter-connecting communication links using a transport protocol suite such as the signaling system 7 (SS7) message transfer part (MTP) protocol. GMSC 106, in turn, communicates with HLR node 108 and AuC node 110 using mobile application part (MAP) signaling protocol messages which may also be transmitted over signaling links using an SS7 MTP transport protocol suite.
Also shown in FIG. 1 is a network monitoring system that includes a central monitoring platform 112 which is connected to communication link probes 114, 116 and 118. More particularly, link probe 114 is adapted to monitor both DTAP and BSSMAP signaling messages communicated between BSS 104 and GMSC 106, sending copies of the DTAP and BSSMAP messages to monitoring platform 112 for analysis and display. Link probe 116 is adapted to monitor the MAP signaling message traffic flowing between GMSC node 106 and HLR node 108, and again sends copies of the monitored messages to platform 112 for analysis and display. In a similar manner, link probe 116 is adapted to monitor the MAP signaling message traffic flowing between GMSC node 106 and AuC node 110, sending copies of the MAP messages to monitoring platform 112 for analysis and display.
As indicated in FIG. 1, the above described wireless network elements function together in concert to provide the intelligent network services typically associated with modern wireless telecommunication networks. As such, inter-communication between these network elements is a very important issue, and is facilitated at least in part by signaling communication links. Currently, the trend within the United States wireless telecommunications industry is towards a signaling infrastructure based on the SS7 and IS-41 protocols. In many countries outside of the United States, a signaling protocol known as global system for mobile communications (GSM) is often employed in wireless communication networks. These two signaling protocols are similar in many respects, and consequently discussions of signaling type communications in this disclosure will be limited to those based on the GSM protocol. It will be appreciated that the present invention, described herein, can be successfully deployed in GSM, Personal Communication Services (PCS) and IS-41-based signaling networks.
Signaling in a wireless or cellular network is employed to implement a number of call processing operations. The term call processing encompasses a wide variety of functions that establish, maintain, and tear down calls to and from mobile subscribers (where a call is defined as a temporary communication between end users for the purpose of exchanging information). Mobile calls include a sequence of events that allocate and assign the resources and signaling channels required to establish build a communication connection. In general terms, the act of call establishment or call setup in a wireless communications network comprises a set of discrete signaling operations that arrange for the allocation and engagement of network resources required for the connection of a mobile call.
In addition to providing the infrastructure for basic call setup and teardown operations as mentioned above, wireless signaling is also responsible for providing general mobility management services. Such services enable a communications network to maintain location and mobile subscriber status information so that end users can make and receive mobile-originated and mobile-terminated calls while moving or roaming from geographic location to another.
The establishment of a mobile call may involve both GSM and Signaling System 7 (SS7) ISDN User Part (ISUP) call control signaling to properly connect the called and calling parties. GSM call signaling is used to obtain the location, status, routing, and any special call treatment information about a mobile subscriber to properly complete mobile-terminated calls. It is also used to obtain call treatment and routing information for mobile-originated calls. This signaling is provided by the GSM intersystem operations. With regard to intersystem handoff, GSM signaling is also used to control the allocation and engagement of inter-MSC voice trunks. A more detailed discussion of GSM and IS-41 mobile signaling can be found in Mobile Telecommunications Networking With IS-41 by Michael D. Gallagher and Randall A. Snyder, McGraw-Hill Publishing 1997 and Signaling System #7 by Travis Russell, McGraw-Hill Publishing 1998.
The brief discussion presented above illustrates the important role of mobile call signaling operations in a wireless communications network and highlights the need for network operators to have the capability of viewing a comprehensive listing of all signaling message traffic associated with a particular mobile call. Such information is particularly useful for troubleshooting, network planning, and billing operations. Previous network monitoring systems, such as monitoring system 112 shown in FIG. 1, have been capable of simultaneously monitoring multiple communication links, where the mobile signaling messages carried on these links are formatted in a variety of signaling protocols. However, automatic correlation of signaling messages generated and communicated between a BSS air-interface and an MSC (e.g., DTAP and BSSMAP) with those signaling messages typically associated with the SS7 protocol (e.g., ISUP, TCAP and MAP) has not previously been available. Those skilled in the art of wireless telecommunication systems will appreciate that the internal structures and parameter contents of BSSMAP, DTAP, ISUP, TCAP and MAP mobile signaling messages differ considerably.
As generally indicated in FIG. 2, the internal structure and parameter content differences primarily exist at a level in the overall protocol stack that is above the MTP transport protocol layer(s). More particularly, shown in FIG. 2 is a typical mobile application part (MAP) message structure 120, a typical ISDN user part (ISUP) message structure 140, a typical DTAP message structure 150, and a typical BSSMAP message structure 160. In these sample structures, it is assumed that each message utilizes an MTP transport protocol which is comprised of an MTP 1 level 122, an MTP 2 level 124, and an MTP 3 level 126. These three MTP levels generally correspond to the physical, data link and network levels, respectively, in the open systems integration (OSI) model developed by the International Standards Organization (ISO). The MTP levels are charged with providing the upper levels of each protocol stack with node-to-node transmission capability, basic error detection/correction capabilities, message sequencing, message routing, message discrimination, and message distribution functionality.
In addition to the MTP layers described above, MAP structure 120 further includes a signaling connection control part (SCCP) level 128, a transaction capabilities application part (TCAP) level 130, and a mobile application part (MAP) level 132. In a similar manner, ISUP structure 140 further includes an ISDN user part (ISUP) level 142. DTAP structure 150 further includes an SCCP level 128, as well as a DTAP level 152. Likewise, BSSMAP structure 162 includes an SCCP level 128, and a BSSMAP level 162. It will be appreciated by those skilled in the art of wireless telecommunication networking that a single mobile call attempt can, and often does, result in the generation of a plurality of messages that are representative of all of the above described mobile signaling message types.
With particular regard to the TCAP level 130, MAP level 132, ISUP level 142, DTAP level 152, and BSSMAP level 162, it will be appreciated that the structure and parameter contents within these levels differ significantly. Consequently, a specific parameter contained in one message type may not necessarily be contained in the structure of another message type. For example, a BSSMAP message associated with a particular mobile call includes a TMSI parameter, while a MAP message associated with the same mobile call does not include a TMSI parameter. This lack of parameter uniformity among mobile signaling message types, combined with the fact that there is not a unique mobile call ID value assigned to each mobile call and subsequently contained in every signaling message associated with that mobile call, makes a complete and comprehensive correlation of all mobile call signaling messages difficult.
Therefore, what is needed is a network monitoring system that is capable of simultaneously monitoring a plurality of communication links in a wireless communications network, including air-interface to MSC links, and automatically correlating and displaying all signaling messages associated with a mobile call.
According to one aspect, the present invention includes a network monitoring system that is capable of simultaneously monitoring a plurality of signaling communication links in a wireless communication network, including air-interface to mobile switching center (MSC) signaling links. The monitoring system is further adapted to automatically correlate all messages associated with a specific call, including related signaling messages observed on an air-interface to MSC communication link. Consequently, a complete and comprehensive record of all relevant signaling messages associated with a specific call is automatically presented to the monitoring system user.
In one embodiment, a network monitoring system of the present invention is adapted to simultaneously monitor a plurality of signaling communication links in a global system for mobile communication (GSM) wireless telecommunications network. As such, the network monitoring system observes and automatically correlates signaling messages associated with a particular user specified call, where the signaling messages are formatted in a variety of different signaling protocols. Such GSM signaling protocols include, but are not limited to base station system management application part (BSSMAP), direct transfer application part (DTAP), mobile application part (MAP), ISDN user part (ISUP), and transaction capabilities application part (TCAP). In a closely related embodiment of the present invention, a network monitoring system is adapted to perform a similar function within an ANSI IS-41 or Personal Communication Services (PCS) type wireless networks.
A network monitoring system of the present invention includes a plurality of communication probes that are adapted to provide non-intrusive monitoring of the signaling communication links to which they are connected. Each communication link probe is communicatively coupled to a central monitoring platform, where collection and correlation processing is performed. The monitoring platform may also implement a user interface for managing any required input/output (I/O) operations. As such, via the user interface a user may specify one or more parameters identifying a particular call or set of calls to be examined. With the necessary call parameters specified, the network monitoring system is adapted to automatically collect, correlate and display all signaling messages indicated by the specified call parameters. Such functionality allows a complete and comprehensive call trace to be automatically performed and displayed, where the results of the trace include relevant signaling messages collected from all monitored communication links.
It is of particular significance that the automatically generated call trace output produced by the network monitoring system of the present invention includes call signaling messages that are communicated between an air-interface or base station system (BSS) and an associated mobile switching center (MSC).
It is also significant that the network monitoring system of the present invention does not require that all signaling message traffic on a signaling link during a given time interval be reported to a central processing platform in order to perform a call trace operation. Instead a network monitoring system of the present invention employs a pre-determined sequence of signaling message filter criteria which are selectively downloaded to a plurality of link monitoring modules, so as to effectively use information contained in a first located signaling message associated with a call trace to search for a second signaling message associated with the same call trace.
Accordingly, it is an object of the present invention to provide a network monitoring system that is capable of simultaneously monitoring a plurality of GSM signaling communication links, including a BSS to MSC signaling communication link, and automatically correlating all signaling messages associated with a user specified call or calls.
It is another object of the present invention to provide a monitoring system for automatically generating and displaying correlated call trace information associated with a specific call or set of calls in a GSM wireless telecommunication network.
It is another object of the present invention to provide a monitoring system for automatically generating and displaying correlated call trace information associated with a specific call or set of calls in an ANSI IS-41 wireless telecommunication network.
It is another object of the present invention to provide a monitoring system for automatically generating and displaying correlated call trace information associated with a specific call or set of calls in a PCS wireless telecommunication network.
It is another object of the present invention to provide a monitoring system that facilitates independent dynamic filtering of signaling message traffic at each signaling link monitoring module or probe.
It is another object of the present invention to provide a monitoring system that does not require that all signaling message traffic on a signaling link during a given time interval be reported to a central correlating platform in order to perform a call trace operation.
It is another object of the present invention to provide a monitoring system that employs a pre-determined sequence of signaling message filter criteria, so as to effectively use information contained in a first located signaling message associated with a call trace to search for a second signaling message associated with the same call trace.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow.